
//自己实现双向链表
public class MyLingkedList {
    static class ListNode {
        public int val;
        public ListNode prev;//前驱节点
        public ListNode next;//后继节点

        public ListNode(int val) {
            this.val = val;
        }

        public ListNode head;//标志头节点
        public ListNode last;//标志尾结点

        //头插法
        public void addFirst(int data) {
            ListNode node = new ListNode(data);
            if(head == null){
                //判断是不是第一次进行插入节点
                head = last = node;
            }else{
                node.next = head;
                head.prev = node;
                head = node;
            }
        }

        //尾插法
        public void addLast(int data) {
            ListNode node = new ListNode(data);
            if (last == null){
                //判断是不是第一次插入节点
                head = last = node;
            }else {
                last.next = node;
                node.prev = last;
                last = node;
            }
        }

        //检查index的合法性
        private void checkIndex(int index){
            if (index < 0 || index > size()){
                throw new IndexNotLegalExpection("index位置不合法!");
            }
        }

        //找到index位置
        private ListNode findIndex(int index){
            ListNode cur = head;
            while(index != 0){
                cur = cur.next;
                index --;
            }
            return cur;
        }

        //任意位置插入,第一个数据节点为0号下标
        public void addIndex(int index, int data) {
            try {
                checkIndex(index);
            }catch (IndexNotLegalExpection e){
                e.printStackTrace();
            }

            if(index == 0){
                //头插
                addFirst(data);
                return;
            }

            if(index == size()){
                //尾插
                addLast(data);
                return;
            }

            //找到index位置
            ListNode cur = findIndex(index);
            ListNode node = new ListNode(data);

            //开始绑定节点
            node.next = cur;
            cur.prev.next = node;
            node.prev = cur.prev;
            cur.prev = node;
        }

        //查找是否包含关键字key是否在单链表当中
        public boolean contains(int key) {
            ListNode cur = head;
            while (cur != null) {
                if (cur.val == key) {
                    return false;
                }
                cur = cur.next;
            }
            return true;
        }

        //删除第一次出现关键字为key的节点
        public void remove(int key) {
            ListNode cur = head;
            while(cur != null){
                if(cur.val == key){
                    //开始删除
                    if(cur == head){
                        head = head.next;
                        if (head != null){
                            //head = null证明链表只有一个节点
                         head.prev = null;
                        }else{
                            last = null;
                        }
                    }else {
                        cur.prev.next = cur.next;
                        if (cur.next == null) {

                            last = last.prev;
                        } else {
                            cur.next.prev = cur.prev;
                        }
                    }
                    return;//删除完一个就结束运行
                }
                    cur = cur.next;
            }
        }

        //删除所有值为key的节点
        public void removeAllKey(int key) {
            ListNode cur = head;
            while(cur != null){
                if(cur.val == key){
                    //开始删除
                    if(cur == head){
                        head = head.next;
                        if (head != null){
                            //head = null证明链表只有一个节点
                            head.prev = null;
                        }else{
                            last = null;
                        }
                    }else {
                        cur.prev.next = cur.next;
                        if (cur.next == null) {

                            last = last.prev;
                        } else {
                            cur.next.prev = cur.prev;
                        }
                    }
                }
                cur = cur.next;
            }
        }

        //得到单链表的长度
        public int size() {
            int count = 0;
            ListNode cur = head;
            while (cur != null) {
                count++;
                cur = cur.next;
            }
            return count;
        }

        //遍历双向链表
        public void display() {
            ListNode cur = head;
            while(cur != null){
                System.out.print(cur.val + " ");
                cur = cur.next;
            }
            System.out.println();
        }

        //清空双向链表
        public void clear() {
            ListNode cur = head;
            while(cur != null){
                ListNode curN = cur.next;
                cur.prev = null;
                cur.next = null;
                cur = curN;
            }
            head = last = null;
        }
    }
}
